Mr. W. Brown on the Oscillations of the Barometer. 28 1 



a half later than that at the Orkneys ; and as the observation at 

 3 p.m. at Belfast shows that it occurred between these hours, 

 the difference in time accounts for part of the difference in the 

 variation of the barometer; but in accordance with this view 

 of the direction of its motion, we observe that the greatest 

 depression of the barometer, as shown by the observations, is 

 at Glasgow, and therefore, if not precisely there, it must be 

 somewhere between this and the Orkney islands, and hence 

 it is that the south wind during these storms very seldom 

 extends to the north of Scotland, and that the north wind is 

 generally prevalent there; and when it is not, the south wind 

 is very inconstant, as there is always a northerly direction 

 given on the same locality, excepting when the wind is simply 

 stated east, when there can be little doubt it was from the 

 north of that point ; and if not so, it at least shows that the 

 south wind had little strength. On the 23rd and 24th, how- 

 ever, the days on which the principal depression of this period 

 occurred, the north wind in the north is well-marked, whilst 

 the south wind is blowing in the south. The latter of these 

 storms offers an example of the case of § 16, but one in which 

 there is a more equable division between both portions of the 

 storms of § 15. 



The two remaining days of the period represent by simi- 

 larity, the remaining portion of the month not included in the 

 observations given; the weather continued stormy, and the 

 barometer fluctuating according to the prevalence of the north 

 or south wind, the north however being on the whole pre- 

 dominant, so that the barometer attained its mean height on 

 the 1st of December. 



As a very remarkable depression of the barometer occurred 

 on the 13th of January, 1843, I included the first fifteen days 

 of this month in my collection of observations, but with the 

 exception of the storm which occasioned that depression, 

 they do not offer anything sufficiently worthy of notice, after 

 what has already been given, to make it necessary to insert 

 them here. That storm however I notice particularly, because 

 it presents an additional illustration of the action of the storms 

 of § 16, its phaenomenaconfirming the account given of storms, 

 derived from a consideration of those of the 10th and 11th of 

 November 1842. It advanced to the north of England from 

 a line running somewhat in the direction from Cork to Ply- 

 mouth ; thus at Plymouth it began at 1 1 p.m. of the 12th, and 

 at North Shields about half an hour after 5 a.m. of the 13th, 

 six and a half hours later ; but in the south its progress to- 

 wards south-east, or its recession along the line c C of fig. 3, 

 is well-marked, for it began at Cork at 7 p.m. of the 12th, 



